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Philadelphia Weekend Weather and Storm Forecasts

Glenn F. Schreiber DMD and Glenn Schreiber is theweatherguy writing about Philadelphia Weather [radar] [surface map] [disclaimer]

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Glenn F Schreiber
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Sun, 13 Jan 2008
Storm Update - Sun Late Afternoon
Temperatures are as high at ground level as predicted by the models. The freezing line was well into NY State, with 40s extending into the Poconos.
Here are the trends as of 5PM
Latest NAM model (1 PM run) has temperatures higher.
Amount of precipitation falling (QPF values) has fallen to about to about 0.50 inches water.
The precipitation reached us as expected. The storm is a rapid mover.

There's little to no really cold air.
This looks like a mostly rain event now, with wet snow mixing in after midnight, but little accumulation expected in Philadelphia or the immediate suburbs. The MOS (model output statistics) doesn't predict a changeover to snow until the early morning hours.

posted: Jan 13 2008 at 6:32 pm

[/weather/jan08] permanent link

Storm Update - Sun AM [2]
The models are still showing temps above freezing in the immediate Philadelphia area for Sunday evening and night. So it might fall as wet snow as the evening progresses. Predicting accumulations in this scenario isn't really possible, but if the models are correct about the surface temps, this won't be much of a storm, except a 1 -2 inch layer of wet snow
Here are the trends as of 11AM
Upper atmosphere temps are remaining cold enough to support snow, BUT ground temps remain above freezing.
Amount of precipitation falling (QPF values) has fallen to about 0.6 inches water.
The precip will likely reach us between 5 and 7 PM. The storm is a rapid mover.

Less precipitation means dynamic cooling less likely.
Sun 1/13: Some sun early, becoming cloudy early afternoon. Precipitation begins as rain or rain mixed with snow about 5-7PM. Likely becoming all very wet snow later. According to the models, the best guess is an 1-2 inch accumulation in Philadelphia more in the far north and northwest. High 47.

posted: Jan 13 2008 at 11:59 am

[/weather/jan08] permanent link

Storm Update - Sun AM
The models are still showing temps above freezing in the immediate Philadelphia area for Sunday evening and night. The statistical models also show less than a 40% chance of snow for the immediate PHL area as well, with probabilities increasing near Allentown. Significant snow is possible in the far northern areas. That said, the temperatures above 2000 feet support snow. So it might fall as snow and then melt or mix with rain in the lower part of the atmosphere. Predicting accumulations in this scenario isn't really possible, but if the models are correct about the surface temps, this won't be much of a storm, except for the heavy rain mixed with snow.
Here are the trends as of 7AM
Upper atmosphere temps are remaining cold enough to support snow, BUT ground temps above freezing.
Amount of precipitation falling (QPF values) are as high as over 1.0 inches water, according to the GFS. The NAM has joined the GFS with about 1.0 inches of water.
The precip will likely reach us between 5 and 7 PM. The storm is a rapid mover.

Extremely heavy precip falls in a six hour period --Most of the precipitation falls before 1AM. Will dynamic cooling bring temps down lower than predicted by the models? Don't know.

The storm depends on a transfer of energy between a low in the Great Lakes and a developing low, a situation often missed by the models. There is no 'large cold high' expected to move in behind the coastal low.
This storm is the toughest one in awhile for me to predict: the temperature profile predicted by the models of this storm is different than most other coastal storms. If the models are correct, this is going to be a mostly rain to snow with just an inch or two accumulating in Philadelphia. (more north and west). If the models are overestimating the ground temperatures (which they might be doing) we could be clobbered. I never try to outguess the models... Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as rain or rain mixed with snow about 5-7PM. Likely becoming all very wet snow later. According to the models, the best guess is an inch or two accumulation in Philadelphia. If the models are wrong about temps, we could be clobbered with much more. High 43.

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posted: Jan 13 2008 at 8:25 am

[/weather/jan08] permanent link

Disclaimer: I am not a meteorologist and provide this information as a hobby and for entertainment (mostly my own :-) . While attempts are made to predict the weather as best as I can, use at your own risk! I am NOT responsible for any direct or indirect consequential injury/damages due to your use of these forecasts. Always check the NWS Official Forecast for your final plans.

The weatherguy.net home page has been visited times since October 2003.

theweatherguy's website
		Philadelphia Weekend Weather and Storm Forecasts
Glenn F. Schreiber DMD and Glenn Schreiber is theweatherguy writing about Philadelphia Weather [radar] [surface map] [disclaimer]
	About this blog theweatherguy's website, "Thoughts and comments on Philadelphia Weather and Daily Life." Glenn F Schreiber aka "theweatherguy" Photos Weather Definitions Copy link for RSS feed Links These are a few of my favorite links. National Weather Service Official Forecasts Meteorology Glossary Archives Weather Archives: 13: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 12: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 11: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 10: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 09: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 08: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 07: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 06: Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 05: Apr May Jun July Aug Sept Oct Nov Dec Commentary: Miscellaneous Find	Sun, 13 Jan 2008 Storm Update - Sun Late Afternoon Temperatures are as high at ground level as predicted by the models. The freezing line was well into NY State, with 40s extending into the Poconos. Here are the trends as of 5PM Latest NAM model (1 PM run) has temperatures higher. Amount of precipitation falling (QPF values) has fallen to about to about 0.50 inches water. The precipitation reached us as expected. The storm is a rapid mover. There's little to no really cold air. This looks like a mostly rain event now, with wet snow mixing in after midnight, but little accumulation expected in Philadelphia or the immediate suburbs. The MOS (model output statistics) doesn't predict a changeover to snow until the early morning hours. posted: Jan 13 2008 at 6:32 pm [/weather/jan08] permanent link Storm Update - Sun AM [2] The models are still showing temps above freezing in the immediate Philadelphia area for Sunday evening and night. So it might fall as wet snow as the evening progresses. Predicting accumulations in this scenario isn't really possible, but if the models are correct about the surface temps, this won't be much of a storm, except a 1 -2 inch layer of wet snow Here are the trends as of 11AM Upper atmosphere temps are remaining cold enough to support snow, BUT ground temps remain above freezing. Amount of precipitation falling (QPF values) has fallen to about 0.6 inches water. The precip will likely reach us between 5 and 7 PM. The storm is a rapid mover. Less precipitation means dynamic cooling less likely. Sun 1/13: Some sun early, becoming cloudy early afternoon. Precipitation begins as rain or rain mixed with snow about 5-7PM. Likely becoming all very wet snow later. According to the models, the best guess is an 1-2 inch accumulation in Philadelphia more in the far north and northwest. High 47. posted: Jan 13 2008 at 11:59 am [/weather/jan08] permanent link Storm Update - Sun AM The models are still showing temps above freezing in the immediate Philadelphia area for Sunday evening and night. The statistical models also show less than a 40% chance of snow for the immediate PHL area as well, with probabilities increasing near Allentown. Significant snow is possible in the far northern areas. That said, the temperatures above 2000 feet support snow. So it might fall as snow and then melt or mix with rain in the lower part of the atmosphere. Predicting accumulations in this scenario isn't really possible, but if the models are correct about the surface temps, this won't be much of a storm, except for the heavy rain mixed with snow. Here are the trends as of 7AM Upper atmosphere temps are remaining cold enough to support snow, BUT ground temps above freezing. Amount of precipitation falling (QPF values) are as high as over 1.0 inches water, according to the GFS. The NAM has joined the GFS with about 1.0 inches of water. The precip will likely reach us between 5 and 7 PM. The storm is a rapid mover. Extremely heavy precip falls in a six hour period --Most of the precipitation falls before 1AM. Will dynamic cooling bring temps down lower than predicted by the models? Don't know. The storm depends on a transfer of energy between a low in the Great Lakes and a developing low, a situation often missed by the models. There is no 'large cold high' expected to move in behind the coastal low. This storm is the toughest one in awhile for me to predict: the temperature profile predicted by the models of this storm is different than most other coastal storms. If the models are correct, this is going to be a mostly rain to snow with just an inch or two accumulating in Philadelphia. (more north and west). If the models are overestimating the ground temperatures (which they might be doing) we could be clobbered. I never try to outguess the models... Sun 1/13: Some sun early, becoming cloudy late morning. Precipitation begins as rain or rain mixed with snow about 5-7PM. Likely becoming all very wet snow later. According to the models, the best guess is an inch or two accumulation in Philadelphia. If the models are wrong about temps, we could be clobbered with much more. High 43. Like these forecasts? Improve my Yahoo ratings by clicking on an ad of interest at the top of the page! If you receive this report via RSS feed, please visit the site http://theweatherguy.net and click. Thanks! posted: Jan 13 2008 at 8:25 am [/weather/jan08] permanent link Disclaimer: I am not a meteorologist and provide this information as a hobby and for entertainment (mostly my own :-) . While attempts are made to predict the weather as best as I can, use at your own risk! I am NOT responsible for any direct or indirect consequential injury/damages due to your use of these forecasts. Always check the NWS Official Forecast for your final plans. The weatherguy.net home page has been visited times since October 2003.